This application claims the priority of British Application Nos. 0014699.3 filed Jun. 15, 2000 and 0016575.3 filed Jul. 5, 2000, the disclosures of both applications being incorporated herein by reference.
The present invention relates to a head-rest, and more particularly relates to a head-rest for a vehicle seat.
The present invention seeks to provide a head-rest for a vehicle seat, and more particularly seeks to provide a head-rest adapted to respond to a rear impact of the vehicle in which the vehicle seat is mounted, in order to minimise the risk of whiplash injury to the occupant of the seat.
It is now known that when a vehicle is subjected to a rear impact, the occupant of a seat within the vehicle, such as, for example, the driver of the vehicle, may suffer from so-called xe2x80x9cwhiplashxe2x80x9d injuries which may be relatively severe, even if the rear impact is only a low velocity impact.
The reason for this is that, when a rear impact occurs to a stationary vehicle, for example, if a following vehicle fails to brake and runs into the back of the stationary vehicle, the stationary vehicle is given a very sudden acceleration. Consequently the floor pan and the seats of the vehicle tend to move forwardly very quickly. The posterior and torso of an occupant of a seat in the vehicle also tend to start moving forward very swiftly, since they are moved forwardly by their engagement with a seat in the vehicle. However, typically the head of an occupant of the vehicle is not in contact with anything and thus, during the initial stages of the rear impact, the torso and lower part of the neck of the occupant of the vehicle tend to move forwardly, whilst the head tends to remain in its initial position.
Of course, the forward movement of the lower part of the neck causes the neck itself to enter a curved state, and then, when the neck is in the curved state, the continuing forward movement of the torso of the occupant of the seat tends to begin to impart a forward motion to the head of the occupant. However, this forward motion is associated with a twisting motion of the head. The head is then given a forward motion purely as a consequence of the forward movement of the torso of the occupant of the vehicle.
It is this chain of events that leads to the xe2x80x9cwhiplashxe2x80x9d injury.
The present invention seeks to provide the head-rest which will reduce the risk of xe2x80x9cwhiplashxe2x80x9d injuries occurring.
According to this invention there is provided a head-rest arrangement for a seat of the motor vehicle, the head-rest comprising a rear part adapted to be mounted on the seat, and a front part, the front part being releasably connected to the rear part and being adapted to move forwardly relative to the rear part, in response to a signal, and means being provided to resist subsequent rearward movement of the front part, relative to the rear part, once the front part has moved forwardly relative to the rear part, the means to resist subsequent rearward movement being adapted to convert energy to a form in which the energy is no longer available to bias the front part forwardly again.
Preferably the front part of the head-rest is releasably connected to the rear part by releasable connection means responsive to said signal, means being provided to bias the front part forwardly relative to the rear part.
Conveniently the front part is connected to the rear part by means of a mechanical linkage incorporating two elongate link elements, each link element having one end thereof pivotally connected to the rear part of the head-rest and each link element having the other end thereof pivotally connected to the front part of the head-rest.
Advantageously the link elements are initially substantially parallel.
Preferably the means to bias the front part of a head-rest forwardly comprise a resilient element extending between the rear part of the head-rest and the front part of the head-rest.
Conveniently the resilient element is in the form of a spring.
Advantageously the resilient element extends between the point of pivotal connection of one link element and the rear part of the head-rest, and the point of pivotal connection between the other link element and the front part of the headrest.
In one embodiment the means to resist rearward movement comprise a deformable member, the deformable member being adapted to be deformed in response to rearward movement of the front part of the head-rest subsequent to the initial forward movement of the front part of the head-rest.
Conveniently the deformable member comprises an elongate member, part of the deformable member surrounding, or partly surrounding guide means mounted on one part of the head-rest, another part of the deformable member engaging retaining means provided on the other part of the head-rest.
Advantageously guide means comprise means defining an outer surface which is of at least part-circular form, around which the deformable member passes, and the retaining means comprise means adapted releasably to retain part of the deformable member.
Preferably the retaining means comprise a pivotally mounted element defining a passage therethrough, and guide means, the element being associated with means providing a rotational bias, the arrangement being such that movement of the deformable member through the passage tends to rotate the element to such a position that the guide means engage the deformable member to guide the deformable member through the passage, and movement in the opposite direction facilitates a rotational movement of the blocking element to a position in which there is frictional engagement between the deformable member and the passage.
In one embodiment the means providing a rotational bias comprise a spring extending from the element to a hook.
In another embodiment the means providing a rotational bias comprise a spring within a bore in the element, one end of the spring engaging the deformable member.
In an alternative embodiment the means adapted to absorb energy comprise a hydraulic shock-absorber.
Conveniently means are provided to restrict the degree of forward movement of the front part of the head-rest.
Advantageously a sensor is provided to generate said signal in response to a rear impact. Such a sensor may be a sensor adapted to generate an electrical signal or may be a sensor adapted to generate a mechanical signal such as a pendulum device or a so-called xe2x80x9cstanding manxe2x80x9d device.